 English |
|
|
|
|
|
|
|
| LTC3809-1_15 Datasheet, PDF (1/24 Pages) Linear Technology – No RSENSE, Low Input Voltage, Synchronous DC/DC Controller with Output Tracking | |||
| |||
|
LTC3809-1
No RSENSETM, Low Input
Voltage, Synchronous DC/DC
Controller with Output Tracking
FEATURES
n Programmable Output Voltage Tracking
n No Current Sense Resistor Required
n Constant Frequency Current Mode Operation for
Excellent Line and Load Transient Response
n Wide VIN Range: 2.75V to 9.8V
n Wide VOUT Range: 0.6V to VIN
n 0.6V ±1.5% Reference
n Low Dropout Operation: 100% Duty Cycle
n Selectable Burst Mode®/Pulse-Skipping/Forced
Continuous Operation
n Auxiliary Winding Regulation
n Internal Soft-Start Circuitry
n Selectable Maximum Peak Current Sense Threshold
n Output Overvoltage Protection
n Micropower Shutdown: IQ = 9μA
n Tiny Thermally Enhanced Leadless (3mm à 3mm)
DFN and 10-lead MSOP Packages
APPLICATIONS
n 1- or 2-Cell Lithium-Ion Powered Devices
n Notebook and Palmtop Computers, PDAs
n Portable Instruments
n Distributed DC Power Systems
DESCRIPTION
The LTC®3809-1 is a synchronous step-down switching
regulator controller that drives external complementary
power MOSFETs using few external components. The
constant frequency current mode architecture with MOSFET
VDS sensing eliminates the need for a current sense resistor
and improves efï¬ciency.
Optional Burst Mode operation provides high efï¬ciency
operation at light loads. 100% duty cycle provides low
dropout operation, extending operating time in battery-
powered systems. Burst Mode is inhibited when the MODE
pin is pulled low to reduce noise and RF interference.
The LTC3809-1 allows either coincident or ratiometric
output voltage tracking. Switching frequency is ï¬xed at
550kHz. Fault protection is provided by an overvoltage
comparator and a short-circuit current limit comparator.
The LTC3809-1 is available in tiny footprint thermally
enhanced DFN and 10-lead MSOP packages.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst
is a registered trademark of Linear Technology Corporation. No RSENSE is a trademark of
Linear Technology Corporation. All other trademarks are the property of their respective
owners. Protected by U.S. Patents including 5481178, 5929620, 6580258, 6304066,
5847554, 6611131, 6498466. Other Patents pending.
TYPICAL APPLICATION
High Efï¬ciency, 550kHz Step-Down Converter
VIN
IPRG
VIN
2.75V TO 9.8V
10μF
MODE
TG
59k
LTC3809-1
VFB
SW
15k
ITH
BG
187k
470pF
RUN
GND
2.2μH
47μF
VOUT
2.5V
2A
38091 TA01
Efï¬ciency and Power Loss vs Load Current
100
10k
EFFICIENCY
VIN = 3.3V
90
1k
VIN = 5V
VIN = 4.2V
80
100
TYPICAL POWER
70
LOSS (VIN = 4.2V) 10
60
50
1
1
FIGURE 8 CIRCUIT
VOUT = 2.5V
0.1
10
100
1k
10k
LOAD CURRENT (mA)
38091 TA02
38091fc
1
|
▷ |
German
Russian
Spanish
Italian
Polish
Chinese
Japanese
Korean
French
Portuguese